This invention relates to an indicating circuit for a computer flash device which interrupts a flash to obtain proper illumination.
One type of such computer flash unit emits light from a flash tube and senses light reflected from the object with a light sensing element so that as soon as the amount of light sensed reaches a predetermined value, the emission from the flash tube is interrupted.
In such computer flash units, the flash runs out before sufficient light has been emitted to illuminate comparatively distant objects.
Conventional computer flash units do not indicate whether a proper flash has been produced. Hence, the photographer is not informed of an under-exposure until the film has been developed.
Japanese Patent Publication No. Sho 52-8186 proposes an indicating device with an indicating lamp that lights for a predetermined time determined by a monostable multivibrator in response to a corroborating signal that occurs when the flash has stopped. This indicates proper flash emission immediately after a photograph has been taken.
While this device solves some problems, other problems remain. For example, if the next flash quickly follows the first flash, and produces its corroborating signal while the indicating lamp is lit, the corroborating signal enters the multivibrator which produces no indication in response to this confirming signal. Hence, this corroborating signal is substantially neglected and fails to indicate whether a proper flash has been emitted.